Diffuse lesion in the splenium of the corpus callosum in patients with methyl bromide poisoning

Reversible Splenial Lesion Syndrome with Some Novel Causes and Clinical Manifestations

Objective Reversible splenial lesion syndrome (RESLES) is a clinical radiological syndrome characterized by a reversible lesion of the splenium of the corpus callosum with a decreased apparent diffusion coefficient (ADC) value. The clinical manifestations of RESLES are diverse. Methods Fifteen cases of adult RESLES patients (10 males and 5 females) were retrospectively selected from the radiology system using the key word "corpus callosum" at a university-affiliated tertiary care hospital between May 1, 2015 and December 31, 2019. The possible precipitating factors, clinicoradiological findings and modified Rankin Scale (mRS) on follow-up were then analyzed. Results The patient ages ranged from 22 to 53 years old. The mean age was 34 years old. The most common neurological symptoms included headache (3/15), dizziness (3/15), first onset of seizure (3/15), paroxysmal blurred vision (2/15), vertigo (2/15), amnesia (2/15), and confused consciousness without seizure (2/15), followed by drowsiness (1/15), paresthesia (1/15), dysmetria (1/15) and dysarthria (1/15). The precipitating factors included infection, seizure, anti-epileptic treatment with levetiracetam, carbamazepine, valproate, hyperglycemia, hypoglycemia, cerebral venous sinus thrombosis, and rabies vaccine injection prior to the onset of RESLES. All cases were carefully followed up and had excellent prognoses. Conclusion RESLES manifests as variety of symptoms with less specificity and precipitating factors. Paroxysmal blurred vision may be a relatively specific symptom of RESLES. Levetiracetam, carbamazepine or valproate could be the cause of RESLES, exposure to the rabies vaccine could be another predisposing factors for RESLES as well. RESLES type 1 was therefore found to be highly "reversible" with an excellent prognosis.

How unclogging a sink can be lethal: case report of an accidental methyl bromide poisoning leading to a multiple organ failure

Methyl bromide (CH3Br) is a colorless and odorless volatile gas, used as an insecticide, fire extinguisher, fumigant, and refrigerant. Although forbidden since 1987 for domestic use, it is still used in industry, for example, to fumigate agricultural fields which are for importation in the United States. Here is the case of a 74-year-old man who was accidentally exposed to methyl bromide after using an old fire extinguisher. Even though he finally survived, he developed a severe multiple organ failure and spent 2 months in intensive care unit. We present in this report all the difficulties we had to diagnose this unusual poisoning.

The neurological effects of methyl bromide intoxication

Used primarily as a fumigant or as a substrate in chemical processes, methyl bromide is a highly toxic gas. The gas is usually absorbed by inhalation and effects on the lungs, gastrointestinal tract, skin, and brain are seen. Numerous instances of acute and chronic neurologic injury have been reported: acute poisoning results in seizures, myoclonus, ataxia or cerebral oedema beginning as early as 30 min after exposure while subacute or chronic intoxication presents with diverse slowly progressive neurological and neurobehavioral symptoms. Serum bromide levels may be elevated, but often return rapidly to normal. Electroencephalography may show frontally-predominant slow waves or polyspikes with following slow wave, and MRI reveals characteristic involvement in the dentate nucleus of the cerebellum, the brainstem, and the splenium of the corpus callosum. Symmetric and selective lesions in characteristic sites are observed on imaging and on histopathological examination. These are likely produced by methylation of intracellular lipids, protein and glutathione; production of toxic metabolites; defective neurotransmitter function; and abnormal oxidative phosphorylation. This article reviews the toxic effects of this gas, the pathophysiology and symptoms of its effects on the nervous system, and characteristic findings on MRI; and presents an illustrative case of methyl bromide intoxication due to exposure at a factory producing the compound commercially.

Prostate cancer and toxicity from critical use exemptions of methyl bromide: environmental protection helps protect against human health risks

BACKGROUND

Although ozone-depleting methyl bromide was destined for phase-out by 2005, it is still widely applied as a consequence of various critical-use-exemptions and mandatory international regulations aiming to restrict the spread of pests and alien species (e.g. in globalized transport and storage). The withdrawal of methyl bromide because of its environmental risk could fortuitously help in the containment of its human toxicity.

METHODS

We performed a systematic review of the literature, including in vitro toxicological and epidemiological studies of occupational and community exposure to the halogenated hydrocarbon pesticide methyl bromide. We focused on toxic (especially chronic) or carcinogenic effects from the use of methyl bromide, on biomonitoring data and reference values. Eligible epidemiological studies were subjected to meta-analysis.

RESULTS

Out of the 542 peer reviewed publications between 1990-2011, we found only 91 referring to toxicity of methyl bromide and 29 using the term "carcinogenic", "neoplastic" or "mutagenic". Several studies provide new additional data pertaining to the mechanistic aspects of methyl bromide toxicity. Few studies have performed a detailed exposure assessment including biomonitoring. Three evaluated epidemiological studies assessed a possible association between cancer and methyl bromide. Overall, exposure to methyl bromide is associated with an increased risk of prostate cancer OR, 1.21; 95% CI (0,98-1.49), P = 0.076. Two epidemiological studies have analyzed environmental, non-occupational exposure to methyl bromide providing evidence for its health risk to the general public. None of the epidemiological studies addressed its use as a fumigant in freight containers, although recent field and case reports do refer to its toxic effects associated with its use in shipping and storage.

CONCLUSIONS

Both the epidemiological evidence and toxicological data suggest a possible link between methyl bromide exposure and serious health problems, including prostate cancer risk from occupational and community exposure. The environmental risks of methyl bromide are not in doubt, but also its health risks, especially for genetically predisposed subjects, should not be underestimated.